Superaudible phonograph recording system



y 1934. J. WEINBERGER 1,957,511

SUPERAUDIBLE PHONOGRAPH RECORDING SYSTEM Filed Oct. 5, 1925 INVENTORJUUUS WE|NBERGER 4Q Helm TORNEY l atented May 8, 1934 UNITED STATES;

PATENT OFFICE Julius Weinberger,

Radio Corporation of Delaware Application October 5, 23 Claims.

The invention concerns phonograph records and methods of making the sameand has for its principal object the provision of a record having uniqueand improved characteristics.

A further object'of the invention is to provide a phonograph record onwhich sounds are recorded in the form of an inaudible frequencymodulated by audible frequencies.

Still another object of the invention is to provide a phonograph recordon which sounds are recorded in the form of superaudible frequenciesmodulated at audible frequencies.

Up to the present time phonograph records have been made using audiblefrequencies only v for the recording. This has been more or lesssatisfactory for the mechanical types of phonographs but with the recentdevelopment of electrical phonographs the use of this type of apparatushas been increased enormously and this developrnent further permits ofgreatly improved reproduction of original sounds. It is proposedaccording to the present invention to record sounds on a record bysubjecting the recording instrument to superaudible vibrations andmodulating the vibrations in conformity with the frequency of the soundwhich it is desired to record. The recording instrument may be vibratedmechanically, electrically, electromagnetically or in any other desiredway but I prefer to use some sort of an electrical system as this canreadily be adapted to the recording process according to the inven i n Arecord made according to this invention could only be reproduced, ofcourse, on a special .35 reproducing machine provided with suitablemeans to convert the modulated superaudible frequencies into audiblesounds. Many different systems could be used for this purpose although Iprefer an electrical system on account of the 4 0 simplicity ofoperation and adaptability to this purpose.

The so called scratch on such arecord would be much less than on thepresent records. Scratch seems to consist mainly of audible frequency,

5 regular impulses given to the reproducer needle by the. groove of therecord. This disturb ance would be reduced on records made according tothe present invention because in the present case the reproducing stylusis al- .5 ways subjected to a steady vibration of high frequency. Thedifference between reproducing records made according to the formermethods and those made according to the present invention resides in thefact that in the former .5 case the. reproducing stylus is subjected toun- New York, N, Y., assignor to America, a corporation of 1925, SerialNo. 60,369

controlled irregularities in the record groove while in the latter casethe stylus is always subjected to a predetermined vibration atsuperaudible frequency. In the former records then an undesiredvibration of audible frequency is present which is avoided to a largeextent by subjecting the stylus to regular superaudible frequencyvibrations.v

A further advantage of records made according to the present inventionresides in the fact that they lend themselves readily and practically toamplification of the reproduced sounds to any desired degree. There is,of course, a definite and rather low limit to the amplification ofsounds obtained from the present day phonograph records by mechanicalreproducing means. The possible amplification maybe increased inelectrical reproducing systems by the use of a suitable number of audiofrequency amplifiers in the shape of vacuum tubes. Amplification by thismethod is superior to that in the mechanical systems but is stilllimited, as the maximum practical amplification obtainable when vacuumtubes are used as audio frequency amplifiers represents a voltageamplification of about 1000. With a record formed. according to thepresent invention, however, amplification can be obtained to any desireddegree as both radio and audio frequencies can be amplified and thecombined amplification is only limited by the ability to keep down thedistortion in the amplification system. Moreover the superaudiblefrequency can be suitably chosen to adapt it readily to amplification.The record groove therefore could be made with very small amplitudes andwith electrical reproduction can be readily amplified to obtain anyrequired volume of sound.

The invention is illustrated by way of example in the accompanyingdrawing in which,

Fig. 1 shows an electricalsystem for engraving records according to theinvention,

Fig. 2 shows in plan view a section of a record, greatlyenlarged, madeaccording to the present invention, and

Fig. 3 shows an electrical reproducing system for playing records madeaccording to the present invention.

Referring to Fig. 1 a record to be engraved is shown at 10 carried by asuitable rotating carriage 11. A recorder 9 of any desired type ismounted in proximity to the record carrier and may be arranged to feedin a radial direction as the record rotates. The recorder is providedwitha stylus 9a which bears against the record and cuts a sp1ral groovein the latter as the recrd rotates. The sounds to be recorded on therecord are impressed on the diaphragm of the microphone 1 which isconnected in series with the primary coil of a transformer 3 and battery2. A self excited vacuum tube oscillator 12 includes in its platecircuit a coil 7 and a battery 12. Its grid circuit includes the coil 6,the secondary of the transformer 3 and the biasing battery l for biasingthe grid potential to its proper value. The secondary coil of thetransformer 3 is shunted by condenser 5 for by-passing high frequenciesaround this coil. The coils 6 and 7 are in proper inductive relationshipto each other to cause the tube 12 to operate as a self excitedoscillator of high frequency oscillations.

The recorder 9 is connected in circuit with a coil 8 also in inductiverelationship with the coil 7. With this arrangement, if no sound wavesare impressed on the microphone 1, the high frequency oscillationsgenerated by the tube 12 will be transferred to the coil 8 and operatethe recorder 9 causing the stylus 9a to vibrate at the frequency of theoscillating tube 12. If sound waves are impressed on the microphone theywill cause a change in current through the primary of the transformer 3thereby causing changing voltages across the secondary of this coil. Asthe secondary of the transformer is in the grid a circuit of theoscillator 12, it will modulate the output of the oscillator inaccordance with the sound waves impressed on the microphone. In thiscase, the stylus 9a will vibrate at the frequency of the oscillator butits vibrations will be modulated in accordance with the sound wavesimpressed on the microphone.

A record formed by this method will have the appearance shown in Fig. 2in which the record and the grooves cut by the vibrating stylus areshown to a greatly enlarged scale. The vibrating stylus cuts grooves inthe shape of the curves 15 consisting of high frequency curves of varying amplitude representing the motion of the stylus. The envelopes ofthese curves represent the audible frequencies with which the highfrequency output of the oscillator is modulated. The envelopes thereforerepresent the frequencies of the sound waves impressed on the microphone1.

As the record represents a modulated high frequency vibration it isclear that some rectifying means must be used to reproduce the soundsrecorded on the record. Such a system is shown in Fig. 3 in which 10represents the record, 16 its rotating carrier, 17 a reproducer of anydesired form provided with a stylus 17a, 19 high frequency vacuum tubeamplifiers, 20 a detector, 21 an audio frequency amplifier and 22 a loudspeaker. The reproducer 17 is connected to the radio frequencyamplifiers and the latter are connected to each other in cascade to theradio frequency transformers 18. The plate circuit of the last highfrequency amplifier is connected to the input of the detector 20 bymeans of the transformer 23. The amplified high frequencies arerectified by the detector and impressed on the audio frequency amplifier21 in whose output circuit is connected the loud speaker 22. Thisarrangement provides for amplifying the superaudible frequencies to. anydesired extent, then detecting them and amplifying the resulting audiofrequencies. The reproducer 17 may be of any desired form such as theelectro-rnagnetic, electro-static, and piezo-electric crystal type butit is desirable that it have a resonant frequency the same as that ofthe carrier frequency on the record. The details of several approvedforms of the reproducer 17 and recorder 9 are shown in my copendingapplication Serial No. 65,135 filed October 27th, 1925. This willincrease the amplitude of the currents supplied to the first highfrequency transformer 18 and improve considerably the operation of thecircuit.

While I have shown my invention as applied to certain specific examples,it is obvious that many modifications will readily occur to thoseskilled in the art, for example, the electrical systems can be replacedby suitable mechanical ones if desired.

I intend to be limited therefore only as indicated by the scope of thefollowing claims:

1. The method of recording sound waves on phonograph records whichconsists in engraving superaudible frequencies modulated with audiblefrequencies thereon.

2. The method of recording sound waves on phonograph records whichconsists in modulating waves of superaudible frequency at thefrequencies of the sound waves and engraving the modulated waves on therecord.

3. The mehod of engraving phonograph records which consists in vibratingthe recording stylus at super-audible frequency and modulating thevibrations at audible frequencies.

4. A phonograph record having sound waves engraved thereon in the formof a modulated super audible frequency.

5. A phonograph record having sound waves engraved thereon in the formof a super-audible frequency modulated at audible frequencies.

6. In combination, an electrical circuit adapted to generate electricaloscillations at a superaudible frequency, means to modulate saidelectrical oscillations at an audio frequency, and

means for engraving said superaudible oscillations of varying amplitudeupon a phonographic record.

'7. In combination, a thermionic valve, 9. superaudible frequencyoscillatory circuit coupled thereto, means for modulating at audiofrequencies the current in said circuit, and an electrically actuatedrecorder for engraving the suepraudible oscillations of varyingamplitude on a phonograph record.

8. The method of recording sound waves upon a phonograph record whichcomprises, vibrating the recording stylus at a constant superaudiblefrequency and at a constant amplitude when no sound waves are beingrecorded, moving the record relatively to the stylus in a predeterminedof the stylus at audio frequencies corresponding to the sound waves tobe re-recorded while maintaining constant the said superaudiblefrequency of vibration of the stylus.

9. A phonograph record having sound waves recorded thereon comprising agroove of wave form having a superaudible frequency, said wave havingvariations in amplitude which correspond to the sound to be reproduced.

10. A phonograph record comprising a stylus its manner, and varying theamplitude of vibration mechanical record thereof engraved withoscillations of relatively higher frequency modulated in accordance withthe sounds to be recorded, which comprises producing from said recordelectrical oscillations corresponding thereto, and converting saidoscillations into sound waves.

13. The method of recording audible sounds which comprises producingelectrical oscillations corresponding to the sounds to be recorded,modulating other electrical oscillations of a relatively higherfrequency in accordance with the first set of oscillations and recordingsaid modulated oscillations as mechanical modifications of a record.

14. The method of recording audible sounds which comprises producingelectrical oscillations correspinding to the sounds to be recorded,modulating other electrical oscillations of a relatively higherfrequency in accordance with the first set of oscillations, andengraving a record blank in accordance with such modulated oscillations.

15. The method of recording audible sounds which comprises producingelectrical oscillations corresponding to the sounds to be recorded,producing a second group of electrical oscillations of superaudiblefrequency, modulating said second group of oscillations in accordancewith said first group, and recording said modulated oscillations asmechanical modifications of a record.

16. The method of recording audible sounds which comprises producingelectrical oscillations corresponding to the sounds to be recorded,producing a second group of electrical oscillations of superaudiblefrequency, modulating said second group of oscillations in accordancewith said first group, and engraving a record blank in accordance withsuch modulated oscillations.

17. The method of recording audible sounds which comprises producingelectrical oscillations corresponding to the sounds to be recorded,producing a second group of electrical oscillations of superaudiblefrequency sufliciently high to be capable of radiation aselectromagnetic waves, modfiating said second group of oscillations inaccordance with said first group, and engraving a record blank inaccordance with such modulated oscillations.

18. The method of reproducing sound from a record engraved withsuper-audible frequency vibrations modulated at sound frequencies whichcomprises producing directly from said record oscillations ofsuper-audible frequency, modulated at sound frequencies, and convertingsaid oscillations into sound waves.

19. Phonographic recording apparatus comprising, in combination, meansfor generating electrical oscillations of a frequency sufficiently highto be modulated at desired sound frequencies, means for modulating saidoscillations in accordance with the sounds to be recorded, and means forengraving a record in accordance with said modulated oscillations.

20. Phonographic recording apparatus comprising, in combination, meansfor generating electrical oscillations of a frequency sufficiently highto be modulated at desired sound frequencies, means for modulating saidoscillations in accordance with the sounds to be recorded, and means forengraving a record in accordance with said modulated oscillations, saidmeans comprising a piezo-electric crystal device.

21. A phonograph record comprising a stylus track having the sounds tobe reproduced recorded therein as vibrations of a frequencycorresponding to that of radiatable electromagnetic waves modulated inaccordance with sound frequencies.

22. Phonograph apparatus for producing from a record electricaloscillations of superaudible frequency modulated at sound frequencies,comprising in combination, a record having sounds engraved on a stylustrack as modulations of a superaudible frequency vibration, and means tobe driven by said record for converting the vibrations produced therebyinto electrical oscillations, said means comprising a piezo-electricdevice.

23. In a piezo electric sound reproducing system, the combination of apiezo electric transmitter arranged to traverse a movable mechanicalmember bearing a sound record and a high frequency simple harmonicvibration record, said high frequency vibration record serving tosensitize said piezo electric transmitter.

JULIUS WEINBERGE

